So far this year 546 people died from tornadoes, making 2011 one of the deadliest tornado years on record.
Tornadoes have struck far and wide across the U.S., hitting Joplin, Mo. (166 deaths), Tuscaloosa, Ala. (36 deaths), and even western Massachusetts.
Historically, however, most tornadoes strike in what is colloquially called Tornado Alley, an area of the country between the Rocky Mountains and Appalachian Mountains. That would include both Joplin and Tuscaloosa, but not western Massachusetts.
So, if there is a pattern to tornado activity just as there is a pattern to hurricane activity, the question that often arises is: Should there be mandatory tornado-safety building codes?
After all, how many of us, when we think of tornadoes, envision one striking a mobile home park, blowing apart those manufactured homes as if they were made of cardboard boxes?
For decades, but especially after Hurricane Andrew in 1992 and the spate of hurricanes in the mid-aughts (2000-09), Florida and other Atlantic and Gulf of Mexico coastal states began implementing stronger hurricane-resistant buildings codes. In 2005, a study by the University of Florida concluded that homes built under the new Florida Building Code, which became effective in 2002, sustained less damage on average than those built to prior codes.
Could stronger building codes help with tornadoes?
I took the question to two of the country’s foremost experts, and, surprisingly, neither of them would give much support to the concept of enhanced building codes.
Tim Reinhold, senior vice president for research and chief engineer at the Institute for Business and Home Safety, knows a thing or two about hurricanes, as the IBHS is based in Tampa, Fla. He also is the person most people turn to when there is talk of tornado-resistant buildings and building codes.
"As early as the 1960s, places like Miami-Dade have been addressing hurricanes, but it became much more of a focus statewide after Hurricane Andrew (23 deaths and $26.5 billion in damages)," said Reinhold. "By the mid-1990s, the state had a decent high-wind code around the coast and in the 2000s Florida tried to make its codes more uniform around the state."
However, Reinhold cautioned, tornadoes are a "different issue." The primary reason being the chances of a tornado striking your home are statistically small.
"If you look at a particular house in Miami-Dade, there is probably a 1-in-200 or 1-in-300 chance a hurricane will strike your home in a given year. Maybe at the tip of Florida, it would be 1-in-50," Reinhold said.
"Even in Tornado Alley, running through the middle of the country, being hit by a tornado is 1-in-10,000, or 1-in-5,000 at best. So, it is off the radar screen in terms of normal design."
Tornado damage is now measured in something called the Enhanced F Scale, with EF1 being the least powerful and EF5 the most powerful. Most people die in tornadoes that are EF3 to EF5 (initial gust at 1/4 of a mile ranging from 148 mph to more than 300 mph). Fortunately, said Reinhold, only about 5 percent to 6 percent of all tornadoes that occur in a given year are in these categories.
So again, the likelihood of your house being hit by such a powerful tornado is very small.
There is another reason why governments are reluctant to improve tornado-resistant building codes: cost.
Ernst Kiesling, a professor of civil engineering at Texas Tech University in Lubbock and executive director of the National Storm Shelter Association, has a storm safe room at his home. Yet he is not on board to make such rooms mandatory. And to design homes to be tornado-safe would not only be near impossible but would add tremendous cost to the construction.
"It is simply not practical to make the whole house safe in case of tornado," he said, and that’s mainly because doors and windows would need to be protected against debris impact.
The best that can be done is to improve what he calls the "connections."
The way a house is built now, roof trusses, joists and rafters are set atop the walls and nailed down. These don’t have much resistance to uplift, and the mode of failure in a tornado is typically that the roof lifts off and the walls have no lateral stability so the whole house collapses. If the garage door blows off, internal pressure intensifies, so the house really doesn’t have a chance.
Kiesling suggests strengthening the connections where the wall attaches to the floor and roof, and also along the ridgelines of the roof.
Other than that, the best option, he advocates, is to design a safe room in the house, which can be done at initial construction or through retrofit at a cost of about $4,000 to $5,000.
Basements are also an option, but only if the basement has a concrete roof.
"So many people with basements have a false sense of security because they have only a beam ceiling," he said. "If the house blows away, now you have a basement open to the sky. We have found a lot of basements filled with debris and even automobiles."
That brings us back to those notorious mobile home parks that seem to be a target of tornadoes. Some states are now requiring mobile home parks to have a storm shelter of some sort.
Unfortunately, human nature is such a contrary thing. Even when such a safe place is available, not everyone uses it in times of storms.
Reinhold tells me this tale: In the recent tornadoes that hit Birmingham, Ala., a community on the north side of the city boasted 110 homes with tornado shelters. Although the storm slid past the community, a powerful tornado did appear imminent, yet only two families used their shelters.
"Either they didn’t perceive there was a risk or they didn’t know about the storm approaching," Reinhold said.